Different voltages in same enclosure

[cppoly]

"Circuits of different voltages can be run in the same raceways or occupy the same spaces (enclosures, equipment) providing that the voltage is less than 600 volts and the conductors each have insulation ratings greater than or equal to that of the circuit with the highest voltage rating. For example, conductors rated for 300 volts can be run in the same raceway as conductors rated for 600 volts as long as the maximum circuit voltage is 300 volts," from Modern Commercial Wiring book.

From the statement above, for 120V & 277V circuits occupying the same enclosure, it reads to me that both 120V & 277V circuits can exist in the same enclosure, without any special separation. Is this true?

 

[tom baker]

yes with some exceptions for switches/devices supplied from 277 different legs or 277 and 120.
Also note the rules in Arts 200, 210 and 215 for identification of the neutral and phase conductors where different systems are in the same enclosure, box or raceway

 

[cppoly]

So no voltage barrier is required for mixed voltages in the same enclosure as compared with the way that a voltage barrier is required for emergency and normal circuits in the same enclosure?

 

[jusme123]

read 406.4(G) '08 code

 

[templdl]

From my experience this is very common.
The issue comes when there is a need to disconnect power and/or de-energize the panel. If this can't be done through some sort of door interlock scheme then suitable warning labels/signage should clearly notify the technician of the pending danger of energized circuits.